Security Update 2020-005 breaks Swift-based Screen Savers crashing on stack guard for thread 0

Warning: It appears that Security Update 2020-005 is causing trouble with Screen Savers which are built using the Swift Runtime.

Symptoms: after updating to Security Update 2020-005 on macOS 10.14 Mojave:
  • Swift-built screensavers no longer funcion

  • You will get a blank screen when the screensaver activates the first time.

  • After the first time, the screensaver will revert to the default macOS screensaver

  • Attempts to view the screensaver in System Preferences / Desktop & Screen Saver will give a blank page

  • Crash logs indicate that the com.apple.preference.desktopscreeneffect.screeneffects.remoteservice process is crashing (see typical crash log below)



Regression Testing:
  • This happens on macOS 10.14.6 with Security Update 2020-005. We do not know if it affects other versions of macOS

  • This affects personal or commercial screensavers built using iScreensaver ( iScreensaver.com ) but also seems to affect other screensavers such as the swift Clock.Saver found here: https://github.com/soffes/Clock.saver



Typical Crash Log:

Code Block
Process: com.apple.preference.desktopscreeneffect.screeneffects.remoteservice [962]
Path: /System/Library/PreferencePanes/DesktopScreenEffectsPref.prefPane/Contents/Resources/ScreenEffects.prefPane/Contents/XPCServices/com.apple.preference.desktopscreeneffect.screeneffects.remoteservice.xpc/Contents/MacOS/com.apple.preference.desktopscreeneffect.screeneffects.remoteservice
Identifier: com.apple.preference.desktopscreeneffect.screeneffects.remoteservice
Version: 1.0 (1)
Build Info: DesktopScreenEffectsPref-229003000000000~20
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: System Preferences [955]
User ID: 507
Date/Time: 2020-09-26 08:19:16.779 -0700
OS Version: Mac OS X 10.14.6 (18G6032)
Report Version: 12
Anonymous UUID: DA9B5F71-78EB-7DD2-F219-AF6A3A811FC1
Time Awake Since Boot: 1300 seconds
System Integrity Protection: enabled
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_PROTECTION_FAILURE at 0x00007ffeef184ff8
Exception Note: EXC_CORPSE_NOTIFY
Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [962]
VM Regions Near 0x7ffeef184ff8:
MALLOC_SMALL 00007fc640000000-00007fc640800000 [ 8192K] rw-/rwx SM=PRV
--> STACK GUARD 00007ffeeb985000-00007ffeef185000 [ 56.0M] ---/rwx SM=NUL stack guard for thread 0
Stack 00007ffeef185000-00007ffeef985000 [ 8192K] rw-/rwx SM=SHM thread 0
Application Specific Signatures:
Clock
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libsystem_malloc.dylib 0x00007fff79a0fc95 malloc_zone_malloc + 99
1 libsystem_malloc.dylib 0x00007fff79a0fc99 malloc_zone_malloc + 103
2 libsystem_malloc.dylib 0x00007fff79a0fc99 malloc_zone_malloc + 103
3 libsystem_malloc.dylib 0x00007fff79a0fc99 malloc_zone_malloc + 103
4 libsystem_malloc.dylib 0x00007fff79a0fc99 malloc_zone_malloc + 103
[... this stack trace repeats for 511 entries ...]

This has been submitted as FB8745172
Also seen in the very popular Aerial screen saver https://github.com/JohnCoates/Aerial/issues/1107
More info
  • This only seems to affect Mojave (10.14)

  • The bug seems to crop up depending on the order in which you installed Safari 14 and Security Update 2020-005. If you installed Safari 14 after the security update, then everything is fine.

  • see mrmacintosh.com/mojave-2020-005-security-update-causing-major-problems-updated/



Security Update 2020-005 breaks Swift-based Screen Savers crashing on stack guard for thread 0
 
 
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